While many investigators have examined the spatial sensitivity of the human visual system using sine grating stimuli, much less work has been devoted to the question of how complex grating stimuli are processed or encoded. In particular, little is known regarding how the phase relationships among the component spatial frequencies of a complex grating are encoded, discriminated and remembered, even though phase is a stimulus variable which clearly affects visual perception. The proposed research is designed to investigate variables which affect the discrimination of and memory for phase. Its purposes are (1) to gather basic and badly-needed data and (2) to distinguish among hypotheses regarding possible mechanisms underlying the encoding of phase.